I have a Panasonic PIR sensor (EKMC1603111) and am measuring the voltage between the output pin and ground pin.
- On the green multimeter I read 0v when there is no motion and 3.3v when there is motion (as expected)
- On my new yellow multimeter I read 3.05v when there is no motion and 3.3v when there is motion.
The yellow multimeter has auto-range, the green multimeter does not. To prevent other factors I left the ends of the leads clamped to the PIR sensor and just plugged the leads out off one multimeter and then into the other. The results with different PIR sensors and different (3.3v and 5v) power sources were the same.
Possibly related: I started this debugging process because I connect the PIR sensor to a Wemos D1 Mini board and the GPIO input put read a constant digital HIGH. This was unexpected behavior but made more sense when I measured that the sensor only switches between 3v en 3.3v during motion. It did not make sense anymore when the green multimeter did show it switches between 0v and 3.3v during motion.
Is one of the multimeters wrong? Is it phantom voltage? Is it related to the permanent digital high reading by the ESP8266 board's digital input pin?